So clearly lines 5 and 135 are key. The FAST command blanks the screen and doubles the CPU speed. Output is revealed after the SLOW command is issued. This is only useful in 40-column mode. In 80-column mode, the CPU is always double speed!

I was also surprised by the color palette selected on the 16. I’m pretty new to the 264 series of computers. I know it has a bigger selection of colors than the 128. It seems like you can access more vibrant colors by issuing a second third argument to the COLOR command. The default 16 colors in the graphic mode seem so… Easter-ish.